It is well known that a glass surface reflects approximately 95.5% of the incident light, reducing in fact the energy efficiency of a photovoltaic cell or making it difficult to read a computer or cell phone flat screen.
This reflection of light on a glass surface is explained more generally by the Fresnel relationships which give, for a light ray passing through a diopter under an angle of incidence of 90°, the following reflection (R) and transmission (T) coefficients:R=((n2−n1)/(n2+n1))2; T=4n1*n2/(n2+n1)2 
where n1 and n2 are the reflective indices of the media separated by the diopter.
It is found that R+T=1 (conservation of energy).
For air (n1=1) and glass (n2=1.54), these formulae produce R=0.045 and T=1-R=0.955 (only 4.5% is reflected whereas 95.5% is transmitted).
For a glass strip composed of two faces, there exists a loss which is two times greater, 2×4.5%=9%. This loss of light energy represents a not insignificant portion for a photovoltaic application.
There exist antireflective processes consisting of depositions based on metal oxide, the use of which is relatively complex and expensive. For example, for lenses, mention will be made of the process which consists in depositing, under vacuum (10−5 torr), thin layers of metal oxides with an accuracy of the order of an angstrom. In dust-free chambers, the lenses are first cleaned in washing lines and then dried under ultrasound. They are fitted into supports which will enter treatment chambers. Vacuum is applied in the chambers in order to obtain the evaporation (sublimation) of the oxide at lower temperature. The evaporation can be carried out by the Joule effect by heating the oxide or using an electron gun. It is necessary to perfectly control the quality and the measurement of the vacuum, the evaporation rate and the thicknesses of layers deposited. These thicknesses should, of course, be uniform. There exist other types of less expensive PVD depositions, such as magnesium fluoride MgF2 (index 1.38) and cryolite Na3AlF6 (index 1.35), the refractive indices of which approach the ideal index without, however, reaching it, as may be made possible by the process of the invention.
“Glass” is understood a mean a hard material or alloy which is fragile (brittle) and transparent to visible light. Generally, glass is composed of silicon oxide (silica SiO2) and fluxes, the main constituent of the being sand. Among all the types of glass, the commonest is soda-lime glass. From the physical viewpoint, glass is an amorphous material (that is to say, noncrystalline material) exhibiting the phenomenon of glass transition. Below its transition temperature, which can be very high, glass exists in the glassy state.
This results in a need for a method for the surface treatment of glass materials in order to introduce antireflective properties over a very long period of time, preferably according to methods which can be easily operated on an industrial scale, so as to be able to offer such glass materials in a significant amount and at reasonable costs.
The document U.S. Pat. No. 5,250,098 discloses a process for the durable antireflective treatment in the visible region of a glass material consisting of a bombardment by an ion beam; the ions used are monocharged.